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-rw-r--r--src/boot/efi/initrd.c140
1 files changed, 140 insertions, 0 deletions
diff --git a/src/boot/efi/initrd.c b/src/boot/efi/initrd.c
new file mode 100644
index 0000000..d994ef8
--- /dev/null
+++ b/src/boot/efi/initrd.c
@@ -0,0 +1,140 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <efi.h>
+#include <efilib.h>
+
+#include "initrd.h"
+#include "macro-fundamental.h"
+#include "missing_efi.h"
+#include "util.h"
+
+/* extend LoadFileProtocol */
+struct initrd_loader {
+ EFI_LOAD_FILE_PROTOCOL load_file;
+ const void *address;
+ UINTN length;
+};
+
+/* static structure for LINUX_INITRD_MEDIA device path
+ see https://github.com/torvalds/linux/blob/v5.13/drivers/firmware/efi/libstub/efi-stub-helper.c
+ */
+static const struct {
+ VENDOR_DEVICE_PATH vendor;
+ EFI_DEVICE_PATH end;
+} _packed_ efi_initrd_device_path = {
+ .vendor = {
+ .Header = {
+ .Type = MEDIA_DEVICE_PATH,
+ .SubType = MEDIA_VENDOR_DP,
+ .Length = { sizeof(efi_initrd_device_path.vendor), 0 }
+ },
+ .Guid = LINUX_INITRD_MEDIA_GUID
+ },
+ .end = {
+ .Type = END_DEVICE_PATH_TYPE,
+ .SubType = END_ENTIRE_DEVICE_PATH_SUBTYPE,
+ .Length = { sizeof(efi_initrd_device_path.end), 0 }
+ }
+};
+
+static EFIAPI EFI_STATUS initrd_load_file(
+ EFI_LOAD_FILE_PROTOCOL *this,
+ EFI_DEVICE_PATH *file_path,
+ BOOLEAN boot_policy,
+ UINTN *buffer_size,
+ void *buffer) {
+
+ struct initrd_loader *loader;
+
+ if (!this || !buffer_size || !file_path)
+ return EFI_INVALID_PARAMETER;
+ if (boot_policy)
+ return EFI_UNSUPPORTED;
+
+ loader = (struct initrd_loader *) this;
+
+ if (loader->length == 0 || !loader->address)
+ return EFI_NOT_FOUND;
+
+ if (!buffer || *buffer_size < loader->length) {
+ *buffer_size = loader->length;
+ return EFI_BUFFER_TOO_SMALL;
+ }
+
+ memcpy(buffer, loader->address, loader->length);
+ *buffer_size = loader->length;
+ return EFI_SUCCESS;
+}
+
+EFI_STATUS initrd_register(
+ const void *initrd_address,
+ UINTN initrd_length,
+ EFI_HANDLE *ret_initrd_handle) {
+
+ EFI_STATUS err;
+ EFI_DEVICE_PATH *dp = (EFI_DEVICE_PATH *) &efi_initrd_device_path;
+ EFI_HANDLE handle;
+ struct initrd_loader *loader;
+
+ assert(ret_initrd_handle);
+
+ if (!initrd_address || initrd_length == 0)
+ return EFI_SUCCESS;
+
+ /* check if a LINUX_INITRD_MEDIA_GUID DevicePath is already registered.
+ LocateDevicePath checks for the "closest DevicePath" and returns its handle,
+ where as InstallMultipleProtocolInterfaces only matches identical DevicePaths.
+ */
+ err = BS->LocateDevicePath(&EfiLoadFile2Protocol, &dp, &handle);
+ if (err != EFI_NOT_FOUND) /* InitrdMedia is already registered */
+ return EFI_ALREADY_STARTED;
+
+ loader = xnew(struct initrd_loader, 1);
+ *loader = (struct initrd_loader) {
+ .load_file.LoadFile = initrd_load_file,
+ .address = initrd_address,
+ .length = initrd_length
+ };
+
+ /* create a new handle and register the LoadFile2 protocol with the InitrdMediaPath on it */
+ err = BS->InstallMultipleProtocolInterfaces(
+ ret_initrd_handle,
+ &DevicePathProtocol, &efi_initrd_device_path,
+ &EfiLoadFile2Protocol, loader,
+ NULL);
+ if (err != EFI_SUCCESS)
+ free(loader);
+
+ return err;
+}
+
+EFI_STATUS initrd_unregister(EFI_HANDLE initrd_handle) {
+ EFI_STATUS err;
+ struct initrd_loader *loader;
+
+ if (!initrd_handle)
+ return EFI_SUCCESS;
+
+ /* get the LoadFile2 protocol that we allocated earlier */
+ err = BS->OpenProtocol(
+ initrd_handle, &EfiLoadFile2Protocol, (void **) &loader,
+ NULL, NULL, EFI_OPEN_PROTOCOL_GET_PROTOCOL);
+ if (err != EFI_SUCCESS)
+ return err;
+
+ /* close the handle */
+ (void) BS->CloseProtocol(initrd_handle, &EfiLoadFile2Protocol, NULL, NULL);
+
+ /* uninstall all protocols thus destroying the handle */
+ err = BS->UninstallMultipleProtocolInterfaces(
+ initrd_handle,
+ &DevicePathProtocol, &efi_initrd_device_path,
+ &EfiLoadFile2Protocol, loader,
+ NULL);
+ if (err != EFI_SUCCESS)
+ return err;
+
+ initrd_handle = NULL;
+ free(loader);
+ return EFI_SUCCESS;
+}